1. Field of the Invention
This invention relates generally to voltage multipliers, and more particularly to voltage multipliers adapted to increase the voltage developed across the leads of a C.R.T.'s heater filament to increase the electron emission of the C.R.T.'s cathode.
2. Discussion of the Prior Art
The cathodes of a cathode ray tube (C.R.T.) tend to degrade in electron emission capabilities with time and usage. This will result in gradually decreasing picture tube brightness and clarity until, finally, the C.R.T. must be replaced.
An aging C.R.T. may be rejuvinated by applying an increased voltage to the leads of the heater filament so as to increase the electron emission of the cathodes. In the prior art, this increased voltage was typically supplied to the heater filament leads by a transformer having a higher secondary voltage than that supplied by the original heater filament transformer.
For instance, in U.S. Pat. No. 2,757,316, N. A. Ackerman discloses an apparatus for brightening picture tubes that includes a multitap transformer having a primary connected to a 120 volt A.C. power source and having a plurality of secondaries so that different heater filament voltages can be selected depending upon the condition of the C.R.T. and upon the picture brightness desired by the user. A problem with using an add-on transformer such as disclosed by Ackerman is that the new, higher voltage suddenly supplied by the transformer has a tendency to "burn out" a cold C.R.T. heater filament.
Another problem with using transformers to provide for an increased heater filament voltage is that they are costly and are generally bulky in size.